The plots of the estimated Rt in the most recent weeks are heavily influenced by the effects that the Easter holidays and the gradual relaxation of pandemic mitigation measures have on mobility. Currently, as restrictions are being relaxed we anticipate a very gradually increasing Rt over the coming weeks.. The Rt for five regions have central estimates just above 1 (EE, GL, SE, SW, WM), although these estimates are uncertain. At current levels of incidence, these values of Rt are not a particular concern, though they do require careful monitoring as the national lock-down is gradually relaxed.
The incidence of deaths has continued to fall more sharply than predicted by the model, with a transition to plateau still anticipated. The number of new infections, as the Rt values indicate, is also flat in almost all regions.
The plot of the infection fatality rate (IFR) presents age-specific probabilities of death given infection. It shows an increasing mortality risk from September onwards in all ages until the immunisation programme begins to have an impact in late January. From the end of January we estimate a decreasing IFR in all adult age groups, but most steeply in the older ages. This drop measures the benefits of immunisation against death over and above the benefits against infection. Specifically, there is an estimated fall to a still-high 15%% in the over-75s and 0.5% overall. The overall impact of the immunisation programme can be seen more clearly in the ‘All Ages’ plot, where the precipitous decline in IFR since late January is a product of this efficacy against death but also of the increasing proportion of infections in young people as older age groups are immunised and become protected against infection. The impact of the second immunisation doses becoming widespread will begin to affect this quantity over the coming weeks.
Since the last published report, the estimates of cumulative infection have been revised substantially downwards. This is due to the inclusion of the prevalence data, which have the effect of reducing the number of infections. Nowhere is this more true than in the North West, where estimates of attack rate have fallen from 31% to 18%. London remains the region with the largest levels of cumulative infection to date.
Other indicators (e.g. hospital bed prevalence, reported new cases) continue to suggest a declining epidemic. Prevalence of infection, as estimated by the ONS Community Infections Survey is now around 0.10% in England with some regional heterogeneity. It is hoped that this trend continues as further pandemic measures are progressively relaxed along the government’s roadmap to opening society. We will continue to monitor the situation closely.
Real-time tracking of an epidemic, as data accumulate over time, is an essential component of a public health response to a new outbreak. A team of statistical modellers at the MRC Biostatistics Unit (BSU), University of Cambridge, are working to provide regular now-casts and forecasts of COVID-19 infections and deaths. This information feeds directly to the SAGE sub-group, Scientific Pandemic Influenza sub-group on Modelling (SPI-M), and to regional Public Health England (PHE) teams.
We fit a transmission model (Birrell et al. 2020) to a number of data sources (see ‘Data Sources’), to reconstruct the number of new COVID-19 infections over time in different age groups and NHS regions, estimate a measure of ongoing transmission and predict the number of new COVID-19 deaths.
We use:
Data are stratified into eight age groups: <1, 1-4, 5-14, 15-24, 25-44, 45-64, 65-74, 75+, and the NHS England regions (North East and Yorkshire, North West, Midlands, East of England, London, South East, South West).
Value of \(R_t\), the average number of secondary infections due to a typical infection today.
The percentage of a given group that has been infected.
NB: negative growth rates are rates of decline. Values are daily changes.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 0.01 | -0.01 | 0.03 |
| East of England | 0.00 | -0.04 | 0.04 |
| East Midlands | -0.01 | -0.05 | 0.02 |
| London | 0.01 | -0.03 | 0.04 |
| North East | -0.01 | -0.05 | 0.03 |
| North West | -0.01 | -0.05 | 0.01 |
| South East | 0.00 | -0.04 | 0.03 |
| South West | 0.01 | -0.03 | 0.05 |
| West Midlands | 0.01 | -0.03 | 0.04 |
| Yorkshire and The Humber | -0.01 | -0.05 | 0.03 |
Halving times in days, if a region shows growth than value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | NA | 111.85 | NA |
| East of England | NA | 16.06 | NA |
| East Midlands | 70.24 | 14.08 | NA |
| London | NA | 22.85 | NA |
| North East | 79.28 | 13.51 | NA |
| North West | 46.77 | 13.83 | NA |
| South East | NA | 18.05 | NA |
| South West | NA | 27.00 | NA |
| West Midlands | NA | 23.04 | NA |
| Yorkshire and The Humber | 87.87 | 13.54 | NA |
Doubling times in days, if a region shows decline then the value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 86.06 | 27.33 | NA |
| East of England | 522.06 | 16.98 | NA |
| East Midlands | NA | 27.73 | NA |
| London | 100.34 | 17.15 | NA |
| North East | NA | 26.72 | NA |
| North West | NA | 48.80 | NA |
| South East | 586.44 | 20.83 | NA |
| South West | 58.02 | 14.26 | NA |
| West Midlands | 88.88 | 17.17 | NA |
| Yorkshire and The Humber | NA | 24.09 | NA |
NB: negative growth rates are rates of decline. Values are daily changes.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | -0.02 | -0.03 | -0.01 |
| East of England | -0.02 | -0.04 | 0.02 |
| East Midlands | -0.03 | -0.05 | 0.00 |
| London | -0.01 | -0.04 | 0.01 |
| North East | -0.03 | -0.05 | 0.00 |
| North West | -0.03 | -0.05 | 0.00 |
| South East | -0.02 | -0.04 | 0.01 |
| South West | -0.01 | -0.04 | 0.02 |
| West Midlands | -0.01 | -0.04 | 0.02 |
| Yorkshire and The Humber | -0.02 | -0.05 | 0.00 |
Halving times in days, if a region shows growth than value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 38.94 | 25.85 | 90.35 |
| East of England | 42.16 | 15.56 | NA |
| East Midlands | 27.26 | 14.31 | NA |
| London | 50.82 | 18.03 | NA |
| North East | 25.92 | 13.61 | NA |
| North West | 23.92 | 13.91 | 147.95 |
| South East | 35.55 | 16.05 | NA |
| South West | 81.04 | 18.69 | NA |
| West Midlands | 46.60 | 17.11 | NA |
| Yorkshire and The Humber | 27.45 | 14.28 | NA |
Doubling times in days, if a region shows decline then the value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | NA | NA | NA |
| East of England | NA | 44.86 | NA |
| East Midlands | NA | 196.51 | NA |
| London | NA | 46.26 | NA |
| North East | NA | 209.60 | NA |
| North West | NA | NA | NA |
| South East | NA | 85.20 | NA |
| South West | NA | 28.59 | NA |
| West Midlands | NA | 42.86 | NA |
| Yorkshire and The Humber | NA | 240.98 | NA |
The shaded areas show periods of national lockdown, the green lines the dates (once confirmed) of the steps in the roadmap in the UK Governement’s COVID-19 Response – Spring 2021, and the red line shows the date these results were produced (23 Apr).